60 GEOGRAPHICAL AND LOCAL 



others have two, and one breed, the Icelandic, 

 is distinguished by having four. How these 

 variations have been produced, and by what 

 circumstances they are ruled, has not been as- 

 certained, nor what differences, in other re- 

 spects, obtain between the armed and unarmed 

 varieties. Linne indeed observed, with respect 

 to the polled sheep, which he denominates 

 English sheep, but whether they are strictly 

 entitled to that name is not clear, for in the 

 pillars of Trajan and Antoninus, though there 

 are no polled oxen, there are polled sheep, 

 that their tails and scrotum reach to the knees ; 

 but this does not appear a certain and invariable 

 fact. A young zoologist, when his attention is 

 first arrested by these facts, will probably be 

 inclined to think that animals, exhibiting such 

 striking differences, cannot belong to the same 

 species ; but in the progress of his experience, 

 especially in what takes place in almost all ani- 

 mals that man has taken into alliance with him, 

 he will see reason to change his sentiments. 



Again, the ears of some animals also exhibit 

 differences that might seem to indicate specific 

 distinction. We see this both in the horse and 

 the swine. In the wild horse the ears lie back, 

 in the domesticated or cultivated one they are 

 erect. The horse was not originally a native 

 of America ; but when the Spaniards and other 

 nations obtained a footing in that country, they 



